Anterior mediastinal gastroenteric cyst containing pancreatic tissue influenced the diabetes mellitus status

Abstract

The mediastinal gastroenteric cyst is a rare developmental cyst. In general, the majority of mediastinal gastroenteric cysts are recognized in infancy and are commonly located in the posterior mediastinum. In addition, gastroenteric cysts occasionally contain pancreatic tissue; however, no studies have reported that these cysts influenced the diabetes mellitus status of the patient. We report here an extremely rare case of an adult gastroenteric cyst with pancreatic tissue originating from the anterior mediastinum, influencing the severity of diabetes mellitus in a patient. This case report presents two remarkable findings. First, the location of the gastroenteric cyst (anterior mediastinum) and the patient's age at the time of detection (adulthood) were extremely rare. Secondly, the present case is also unusual in terms of glycometabolism. As this tumour decreased in size, the glycosylated haemoglobin value increased, which suggested a worsening of the patient's diabetes mellitus. The diabetes mellitus further worsened after removal of the tumour.

INTRODUCTION

Mediastinal gastroenteric cyst is a rare developmental cyst. In general, the majority of mediastinal gastroenteric cysts are recognized in infancy and are commonly located in the posterior mediastinum [1–3]. Gastroenteric cysts occasionally contain pancreatic tissue [2, 4], which can influence the patient's blood- sugar level.

We report here an extremely rare case of an adult patient with diabetes mellitus and a gastroenteric cyst with pancreatic tissue originating from the anterior mediastinum.

CASE REPORT

A 51-year old male patient with a fever and chest pain presented with a mediastinal mass, which was suspected to be a mediastinal abscess. The patient had suffered from diabetes mellitus for 21 years. The patient received subcutaneous injection therapy comprising a total of 15 units of insulin aspart and 16 units of insulin glargine. Three months before suspecting a mediastinal abscess, the patient's blood glucose level and glycosylated haemoglobin (HbA1c) were 168 mg/dl and 6.7% (normal range <6.5%), respectively. At the time of admission, laboratory data showed the following: white blood cell count (WBC) of 11410/µl (normal range 3500–8500/µl), C-reactive protein (CRP) of 9.50 mg/dl (normal range 0.00–0.30 mg/dl), blood glucose level of 86 mg/dl and a normal HbA1c of 5.5%. The patient's chest X-ray (Fig. 1a), chest computed tomography (CT; Fig. 1b) and magnetic resonance image findings showed an irregularly shaped and heterogeneously enhanced mass measuring 6 cm and located in the anterior mediastinum. These findings suggested the presence of a mediastinal cystic tumour or mediastinal abscess. The lesion had decreased in size 30 days after antibiotic treatment including sulbactam/ampicillin and clindamycin (Fig. 1c). At this time, blood glucose level and HbA1c were 113 mg/dl and 6.5%, suggesting that the patient's diabetes mellitus status had worsened. Nevertheless, 60 days after starting antibiotic therapy, re-growth of the lesion was found (Fig. 1d). Thus, for a definitive diagnosis, the patient underwent three-port video-assisted thoracoscopic surgery. The tumour, measuring 56 × 44 × 37 mm and located in the right thymus, was adhered to the pericardium. After dissecting this adhesion, extirpation of the tumour with the right thymus was performed (Fig. 2a). Pathological examination revealed the following. (i) Heterotopic gastric tissue with hyperplastic foveolae, pyloric glands (Fig. 2b) and respiratory-type epithelium, and nests of normal pancreatic tissue with Langerhans islets (Fig. 2c) in the thick fibrocollagenous smooth muscle wall of the tumour. Severe active inflammatory infiltration with abscessation and coagulation necrosis in the cyst. (ii) Immunohistochemically, the covering columnar epithelium was positive for human gastric mucin and MUC5Ac. Gastric pyloric glands were positive for MUC6. Some gastrin-positive cells were seen in the columnar epithelium. Nested islet cells were positive for insulin and weakly positive for glucagon. Based on these findings, the tumour was definitively diagnosed as a gastroenteric cyst containing pancreatic tissue and respiratory-type epithelium. The patient had an uneventful postoperative recovery and was discharged from the hospital 6 days after surgery. However, the patient's blood glucose level and HbA1c were 355 mg/dl and 7.9%, respectively, which suggested that the diabetes mellitus status had further worsened 3 months after the operation. Thus, it was necessary to increase the insulin volume (total 17 units of insulin aspart and 17 units of insulin glargine) to treat the patient's diabetes mellitus.

Figure 1:

Chest radiograph and CT findings. (A) Chest radiograph showed a mass in the right lung field. (B) Chest CT showed a large and heterogeneous mass measuring 6 cm in the anterior mediastinum. (C) Chest radiograph showed that the mass had decreased in size. (D) Chest radiograph showed that the mass had regrown.

Figure 2:

Macroscopic and histological findings. (A) The tumour was yellow-white in colour and comprised multiple cysts. It measured 58 × 44 × 37 mm. (B) Heterotopic gastric tissue with hyperplastic foveolae and pyloric glands (C) nests of pancreatic tissue with Langerhans islets were also observed in the thick fibrocollagenous wall (haematoxylin-eosin staining, original magnification ×100).

DISCUSSION

This case report presents two remarkable findings. First, the location of the gastroenteric cyst (anterior mediastinum) and the patient's age at the time of detection (adulthood) were extremely rare. The most frequent position of the gastroenteric cyst is the posterior mediastinum [1–3], and the majority of mediastinal gastroenteric cysts are found during infancy.

Secondly, the clinical course was unique. In the present case, the tumour decreased in size and regrew thereafter. CT revealed that the fluid volume had increased when the tumour regrew. In addition, the patient's diabetes mellitus had clinically improved before treating the mediastinal tumour with antibiotic therapy despite the presence of an inflammatory reaction, including elevated WBC and CRP. The HbA1c value in the symptomatic phase (the tumour had probably increased in size) was low compared with that in the asymptomatic phase (the tumour had not been detected). As this tumour decreased in size, the HbA1c value increased, which suggested a worsening of the patient's diabetes mellitus. The diabetes mellitus further worsened after removal of the tumour. Regarding this mechanism, gastric acid secretion or pancreatic secretion by the tumour cells may have resulted in severe inflammation, and the pancreatic tissue originating from the tumour may have improved the condition of the patient's diabetes mellitus. With antibiotic therapy, the inflammation of the tumour was reduced, consequently reducing the extend of pancreatic tissue therein. Moreover, the surgical removal of the tumour may have resulted in the further worsening of the patient's diabetes mellitus. Wang et al. [5] reported that ectopic pancreatic tissue did not affect blood sugar levels because drainage of the endocrine secretion from the pancreatic cyst into the blood circulation was difficult. Thus, the present case is also very unusual in terms of glycometabolism.

The tumour in this patient histologically comprised gastric tissue, pancreatic tissue, smooth muscle cells and respiratory-type epithelium. Thus, a pancreatic cyst was easily excluded as a differential diagnosis. However, exclusion of other differential diagnoses, especially mediastinal teratoma or dermoid cyst, was necessary. All tumour specimens were carefully histologically examined, and no components suggestive of these diseases were found, such as sebaceous glands, fat tissue, calcification or hair follicles. Thus, we diagnosed this tumour as a gastroenteric cyst containing pancreatic tissue and respiratory-type epithelium, originating from the anterior mediastinum.

In conclusion, we reported here an extremely rare case of a gastroenteric cyst originating from the anterior mediastinum. General thoracic surgeons should keep the diagnosis of gastroenteric cysts in mind, even in the anterior mediastinum.

Conflict of interest: none declared.